This invention relates to an adsorbent material for recovering and removing objectionable substances, in particular, arsenic that are contained in environmental water and liquid wastes such as waste water from plants. The invention also relates to a method of synthesizing the adsorbent material.
Research and development efforts have recently been made on materials capable of trapping metals contained in environmental water bodies such as rivers and the sea and this has led to the discovery that cation exchange resins using phosphoric acid as exchange groups can adsorb metal ions present in rivers, lakes and wastewater from plants (see, for example, Akinori Joh et al., “Cation exchange resins using phosphoric acid as exchange groups—Their selectivity for metal ions and applications” in PHOSPHORUS LETTER, Japanese Association of Inorganic Phosphorus Chemistry, Feb. 1, 2001, vol. 40, pp. 16-21).
Further, the present inventors developed a metal adsorbent material that had a monomer with phosphoryl groups grafted onto a polymeric substrate (see, for example, Japanese Patent Application No. 2002-262502).
In the art of recovering and removing objectionable substances in the environment, particularly arsenic, two major methods have so far been practiced, one relying upon coagulating sedimentation and the other using chelating resins (see, for example, Xiaoping Zhu et al., “Removal of arsenic(V) by zirconium(IV)-loaded phosphoric acid chelating resin” in “SEPARATION SCIENCE AND TECHNOLOGY”, America, Marcel Dekker, Inc., 2001, 36(14), pp. 3175-3189).
However, the conventional adsorbent materials can adsorb arsenic only slowly. If arsenic is recovered and removed by coagulating sedimentation or with the aid of adsorbent materials in bead form, considerable inconvenience in handling has been met during the process of removal or in subsequent operations.
In addition, the conventional arsenic adsorbent materials are mostly synthesized by common radical polymerization and their structure for adsorption of arsenic is so unstable that it is prone to leak out even if it is adsorbed.
According to the Basic Environment Law which provides for the water quality guidelines for public waters, arsenic should not be discharged at concentrations higher than 0.1 ppm and its content in the environment should not exceed 0.01 ppm. Thus, the removal of arsenic is absolutely necessary.